Migration from sysvinit to systemd: reboot fails to complete

[Michael Biebl]

Am 30.12.2016 um 22:16 schrieb Felipe Sateler:
> Well, rebooting from sysvinit to systemd is supposed to work too, so
> it doesn't explain everything. But, your experience appears to uncover
> another bug: for some reason the sysvinit mount scripts will unmount
> /usr! This is a bad idea, as the distinction between / and /usr is not
> relevant anymore (because we now have initramfs), and will stop
> existing after the /usr merge. The question is, why would sysvinit
> unmount /usr, it probably shouldn't.

So, I've setup a split-usr VM and I can reproduce the issue.
If you switch from sysvinit-core to systemd-sysv in one step (i.e.
without the intermediary boot via init=/bin/systemd), the
shutdown/reboot step fails when trying to call the reboot binary (i.e.
systemctl)

/etc/rc6.d/ looks like:
...

> lrwxrwxrwx  1 root root    18 Dez 20 12:46 K07umountfs -> ../init.d/umountfs
> lrwxrwxrwx  1 root root    20 Dez 20 12:46 K08umountroot -> ../init.d/umountroot
> lrwxrwxrwx  1 root root    16 Dez 20 12:46 K09reboot -> ../init.d/reboot

Afaics, /usr is unmounted by umountfs.

Some possible ideas

1/ document that switching from sysvinit-core to systemd-sysv is best
done by first installing systemd, then booting via init=/bin/systemd on
the kernel-command-line, then making the switch permanent by
uninstalling sysvinit-core and installing systemd-sysv
And if you are using a split-usr setup, doing it this way is mandatory

2/ update umountfs to not umount /usr. But then, something needs to
umount /usr later or at least remount it ro. I don't think we can just
leave /usr mounted without risking an unclean fs. Under systemd, the
umount of /usr is done by /lib/systemd/systemd-shutdown.

3/ when switching from sysvinit-core to systemd-sysv, keep a copy of the
(old) /sbin/{reboot,halt,poweroff} in /run and use that in
/etc/init.d/reboot

4/ move liblz4 to /lib.

I don't like 4/ very much, as eventually we have to fix this anyway
(thinking of usrmerge).

Thoughts, other ideas?

Fwiw, I'm personally leaning towards 1/.

Michael
-- 
Why is it that all of the instruments seeking intelligent life in the
universe are pointed away from Earth?

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: OpenPGP digital signature
URL: <http://alioth-lists.debian.net/pipermail/pkg-systemd-maintainers/attachments/20161231/522584b4/attachment-0002.sig>